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  • Title: Achieving Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in GeTe Alloys via Introducing Cu2Te Nanocrystals and Resonant Level Doping.
    Author: Zhang Q, Ti Z, Zhu Y, Zhang Y, Cao Y, Li S, Wang M, Li D, Zou B, Hou Y, Wang P, Tang G.
    Journal: ACS Nano; 2021 Dec 28; 15(12):19345-19356. PubMed ID: 34734696.
    Abstract:
    The binary compound of GeTe emerging as a potential medium-temperature thermoelectric material has drawn a great deal of attention. Here, we achieve ultralow lattice thermal conductivity and high thermoelectric performance in In and a heavy content of Cu codoped GeTe thermoelectrics. In dopants improve the density of state near the surface of Femi of GeTe by introducing resonant levels, producing a sharp increase of the Seebeck coefficient. In and Cu codoping not only optimizes carrier concentration but also substantially increases carrier mobility to a high value of 87 cm2 V-1 s-1 due to the diminution of Ge vacancies. The enhanced Seebeck coefficient coupled with dramatically enhanced carrier mobility results in significant enhancement of PF in Ge1.04-x-yInxCuyTe series. Moreover, we introduce Cu2Te nanocrystals' secondary phase into GeTe by alloying a heavy content of Cu. Cu2Te nanocrystals and a high density of dislocations cause strong phonon scattering, significantly diminishing lattice thermal conductivity. The lattice thermal conductivity reduced as low as 0.31 W m-1 K-1 at 823 K, which is not only lower than the amorphous limit of GeTe but also competitive with those of thermoelectric materials with strong lattice anharmonicity or complex crystal structures. Consequently, a high ZT of 2.0 was achieved for Ge0.9In0.015Cu0.125Te by decoupling electron and phonon transport of GeTe. This work highlights the importance of phonon engineering in advancing high-performance GeTe thermoelectrics.
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